This invention relates to traction enhancing systems, and more specifically to a system for controlling the deployment rate and mixing of traction enhancing agents for use on roadways and the like.
In areas where roadway icing occurs, traction enhancing agents are typically deployed, by a government agency or municipality, for example, in order to increase traction and/or remove ice from a roadway or prevent ice accumulations. Heretofore, such systems typically include a truck carrying a traction enhancing agent, which can comprise sand, salt, liquids or some other agent. In early systems, the traction enhancing agent was dispensed at a constant rate, and an operator had an on/off switch to start and stop the deployment. Such systems had the drawback of an inconsistent or uneven application rate, since when the deployment truck moved faster, less material per unit of road length would actually be applied. Conversely, when the deployment truck was temporarily slowed or stopped while the dispensing mechanism was still activated, an excessive amount of traction enhancing agent would be applied. Excessive application rates required more frequent re-filling of the deployment truck. Further, with traction enhancing agents that raise environmental pollution issues, the minimal amount necessary is desirably employed, in order to reduce the amount of or likelihood of pollution (as well as saving money).
To attempt to solve some of the application rate issues, sensors were added to factor in the relative speed of the deployment vehicle, and then control the application rate based thereon. Still further systems were developed that enabled a set rate of deployment, e.g. weight of material per distance traveled (typically pounds per lane mile in the United States of America). With such systems, an operator had only to set the deployment rate and control the on/off status of the deployment apparatus. Such systems were fine with simple single traction enhancing agent deployment systems. However, more advanced deployment strategies have been developed, including solid traction enhancing agent deployment systems that include pre-wetting of the traction enhancing agent (with a brine, for example) and dispensing of anti-icing chemicals. Such multi-mode systems require more complex control, as the dispensing of anti-icing agents is done prior to ice formation (e.g. when the road surface temperature is above freezing). In the case of dispensing salt as the traction enhancing agent, for example, a pre-wetting brine is desirably applied to the salt at certain road temperature ranges prior to dispensing or concurrently therewith, to increase the likelihood that the salt will immediately stick to the road surface and hasten the melting process. Such pre-wetting adds another factor that the operator of the dispensing truck must control, as road temperature is a critical factor in choosing pre-wetting.
Still further, for certain traction enhancing agents, salt, for example, as the road temperature becomes lower, a point is reached wherein the traction enhancing agent is no longer effective (e.g. the salt will not melt the ice once the temperature drops too low). At such temperatures, the operator must stop deployment of the traction enhancing agent, to avoid waste.
In the past, a second operator was added to a deployment truck, with the first operator's job being limited to driving the truck, and the second operator's job being to operate the dispensing controls, monitoring the outside air temperature, and stopping the deployment if the temperature got too low. However, multiple operators increase the cost, so the trend is to systems that can be operated by a single driver. Further, the air temperature can differ from the road temperature, and the most important factor is the actual road temperature. Still further, having the single driver control multiple aspects of traction enhancing agent deployment increases the chance of mis-deployment or an accident, since the operator can be kept busy just driving, even without having to control and monitor the various functions.